Patent GB-1010206-A (GB)
Title: Branched artificial filaments
Inventor: SCRAGG FREDERICK
IPC: D01D5/42
Filed: 1962-03-09
Abstract: 1,010,206. Making branched filaments. E. SCRAGG & SONS Ltd. Feb. 14, 1963 [March 9, 1962], No. 9082/62. Heading B5B. Branched filaments, i.e. filaments consisting of a main continuous or trunk portion and short branch portions projecting from the main or trunk portion and integral therewith, are made by slitting or punching a web of film to form a predetermined pattern of closely spaced or overlapping rows of slits or holes, stretching the web first longitudinally, then stretching the web transversely to widen the slits in the longitudinal and in the transverse direction, so that the rows of widened slits or holes now form a ladder-like pattern, and slitting the web longitudinally into narrow strips along closely spaced lines cutting across the widened slits or holes so that the " rungs " of the " ladder " are cut and branched filaments are formed, the longitudinal " lanes " or areas of the film formerly between the rows of the slits or holes constituting the " trunk " or main portion of each filament and the severed portions of the " rungs " of the ladders constituting the branches of each filament. The film material may be a synthetic organic thermoplastic linear polymer such as nylon, polyethylene terephthalate, polypropylene or cellulose acetate. The longitudinal stretching of the web may be carried out while the web is heated. As shown in Figs. 17 and 18, the filaments may be made by melt-extruding polymeric material from an extruder 1 through a slot die 3 to form a web of film 4 which after being cooled and solidified by travelling through a short air space is passed between a pair of co-operating slitting rolls 5 and 6 which are driven at a predetermined speed. The roll 6 has a facing of a resilient material such as polyurethane and the roll 5 has sharp blades projecting from its surface which cut rows of slits in the web according to a predetermined pattern. The web is then drawn over and in contact with the concave surface of a heater 7, which is automatically maintained at a constant predetermined temperature, by means of a pair of co-operating draw rolls 8 and 9 which are pressed together and driven at a peripheral speed several times that of the rolls 5 and 6. The slit and longitudinally stretched web is then caused to travel over the curved surface of a transverse bar 10 whose length is considerably greater than the previous width of the web and the web is thereby stretched transversely. The web is thereafter passed under a row of closely spaced circular knives 11 mounted on a shaft by means of which they are rotated at a constant speed, and the web is thereby slit longitudinally into parallel narrow strips having the form of branched filaments which are wound on to a beam 12 resting on a driving roller 13. The web of film may be formed by the extrusion of a solution of a polymeric material which must be solidified by chemical coagulation, in which case the web of film 4 after leaving the extrusion die 4 is sprayed with a coagulating liquid before reaching the rolls 5 and 6. The cutters 11 may be arranged to co-operate with a backing roll to support the web while it is being longitudinally slit. The roll 5 may be provided with heating means if the film material is thermoplastic. The web of film may be cut to form a herring-bone pattern of straight slits as shown in Fig. 1, which after longitudinal stretching of the web of film become widened as shown in Fig. 2. After the transverse stretching step the slits have the shape shown in Fig. 3 in which the dotted lines indicate the lines along which the rotating circular knives 11 cut the web longitudinally into narrow strips. The portions 14 of the strips constitute the trunks of the branched filaments and the cut " rungs " 15 of the " ladders " constitute the branches or side projections of the branched filaments. Figs. 4 and 6 show other patterns of straight slits which may be formed and Figs. 5 and 7 show the expansion of the slits resulting from the drawing of the film and the longitudinal lines along which the web of film is cut into narrow strips. Fig. 8 shows a pattern formed by punching leaf-shaped holes in the web and Fig. 9 the pattern formed after stretching of the web, the dotted lines as before indicating the longitudinal cutting lines. Figs. 10 to 12 show the patterns formed by rows of parallel slits at an angle to the longitudinal axis of the web of film and Figs. 13 to 16 the patterns formed when rows of small round holes are punched in the web.